2002 Sienna P0420, 1135, 1155, still 1135 after replacing A/F senor on bank 1 Options

[2002SiennaZ]

Hello, it's my 2002 Sienna CE with 90,000 miles.

shortly after State Inspection last month, the check engine light went on.

With multimeter, I found the front A/F sensor resistor too low, just 1.5 Ohm. My obd-ii scanner showed me three faults:

P0420 -
P1135 - A/F sendor heater circuit response (bank 1 sensor 1)
P1155 - A/F sendor heater circuit (bank 1 sensor 2)

So I replaced the bank 1 sensor 1 that is located at the front, easy to replace, and cleared the error code. But the engine light went back on after a short while. A recheck now gives only one code:

P1135 - A/F sendor heater circuit response (bank 1 sensor 1)

So I'm puzzled. bank 1 sensor 1 is brand new. How come the other two error codes dissappeared while the p1135, which is about the sensor I just replace, is still there.

It is highly unlikely the newly purchased Toyota part is defective.

Can any more experienced please give me some tip over how to isolate the problem?

it cost over $200 a piece. so I don't want to waste the money to replace the bank 1, sensor 2 which is not even indicated to be bad.

many thanks for any tip.

[2002SiennaZ]

Problem solved. The Bank1 sensor one is not the one at the front of the vehicle, rather the one at the firewall end of the engine.

Lesson learned:

never try to loosen the A/F sensor with an open wrench, it will damage the hex surface and you end up having to bring it to the dealer, who may inturn replace the whole exhaust manifold, at your money!!!, which I almost did.

At one point, I decided I've got to the get the right tool, so went to AutoZone and get a 22mm Oxygen Sensor Removal socket. It then took me 20 minutes to remove the old sensor, and 10 more minutes to install the new one.

Big saving, at least 200 labor, plus potential new exhaust manifold $300

Happy Repair!

[MickeyFouse]

An inexpensive way to troubleshoot further is to just swap the front and rear bank sensors and see if the trouble code changes to the other bank. If it does then you know it is the sensor if not start checking the wiring. Pay special attention to look for corrosion/contamination in the sensor connectors and some important automotive parts.

[wellmax1]

i had the p1135 code on my 2002 van at 100K, it was the back sensor by the fire wall.

I let dealer replace it, did not want to brake exhaust manifold. also pvc valve is in there somewhere close, so replace it while you are at it.

cleared code and no other problems.

was a bit pricey, but have had almost no other problems with van in 115K.
I would buy another new 2002 model if they were still making them.

time for timing belt and plugs (back 3 plugs are a **** too), drive belts etc, have it all done and you are on your way.

I plan on keeping ours to 150K, just made a 600 mile trip and it ran great with 25+ mpg.

[lsac]

According service manual, the resistance of the sensor (P1135) should be in certain range so does voltage. Is it possible to cascade a resistor to adjust the resistance to accepted range so engine light does not come up? This would be a quick and easy solution.

[pstalsania]

I need to change Bank 1 sensor 1. Can you help me finding it? I do not have much experience but I do not want to pay 300 buck for $75 part. When I open hood I see sensor next to radiator. Is that Bank 1 sensor 1? Else How can i find it?

Thanks for help